The present invention generally relates to the field of driving apparatuses for driving electric loads through TRIACs (Triode for Alternating Current). More specifically, the present invention relates to a system for monitoring such driving apparatuses and such electric loads.
TRIACs are typically employed in those applications in which an electric load should be supplied with an adjustable AC power, such as for example in motor speed regulation and temperature control. Making reference to the washing and/or drying appliances, comprising laundry washing and/or drying machines and dishwashers, such electric loads may for example comprise: the drain pump and/or the recirculation pump of a laundry washing machine, a laundry washing and drying machine or a dishwasher; the electric motor for rotating the rotatable drum of a laundry washing and/or drying machine; the heating resistor(s) for heating the washing liquid of a laundry washing machine, a laundry washing and drying machine or a dishwasher; the heating resistor(s) for heating the process air of a laundry drying or a laundry washing and drying machine; the process fan for circulating the process air of a laundry drying or laundry washing and drying machine; the compressor of an heat pump for demoisturizing and heating the process air of a laundry drying or a laundry washing and drying machine; a fan for cooling the compressor of an heat pump for demoisturizing and heating the process air of a laundry drying or a laundry washing and drying machine; a pump for draining condensation water of a laundry drying or a laundry washing and drying machine.
As it is well known to a person skilled in the art, a typical driving apparatus for driving an electric load through a TRIAC comprises a TRIAC connected in series with the electric load between the line and the neutral terminals of an AC power supply, and a triggering circuit connected to the gate terminal of the TRIAC for switching on the TRIAC at an adjustable time (phase angle) after the start of each half-cycle of the AC voltage waveform at the line terminal, thereby altering the actual voltage difference waveform applied between the electric load terminals and so changing its RMS (Root Mean Square) effective value.
U.S. Pat. No. 5,734,289 discloses a circuit arrangement for controlling an alternating current through a TRIAC. The circuit arrangement comprises a TRIAC having a gate terminal and first and second terminals through which an alternating current is supplied, and a threshold detector coupled to the gate terminal of the TRIAC. The threshold detector outputs a signal when the voltage on the gate terminal of the TRIAC is between two predetermined thresholds of opposite polarities. The circuit arrangement further comprises a pulse generator coupled to the threshold detector. The pulse generator is adapted to supply a TRIAC gate pulse to the gate terminal of the TRIAC in response to said signal from the threshold detector, such that TRIAC gate pulses are supplied during zero crossings of the alternating current through the first and second terminals of the TRIAC.
Household and professional appliances typically comprises a number of electric loads adapted to be driven through driving apparatuses comprising a TRIAC. Therefore, it would be highly desirable to monitor the operating condition of said driving apparatuses and of the electric loads, in such a way to detect the occurrence of possible malfunctioning, and, in case a malfunctioning has been detected, to evaluate whether the appliance has to be turned off based on the gravity of the detected malfunctioning.
It is known to provide monitoring circuits adapted to monitor the operating condition of the driving apparatuses, and/or of the electric loads, in order to signal if a malfunctioning of some kind has occurred.
However, the Applicant has found that none of the solutions known in the art are satisfactory, being too expensive, too complex, power-consuming in the stand-by, and/or requiring calibration.